Ion Exchange membranes are an important development of modern technology and are used for example in chlor alkali production and in sensors for chemical analysis. One problem with the use of ion exchange membranes is when a new membrane is used in an application, its performance can be poor until it has a chance to equilibrate in the system, e.g., be thoroughly converted to the hydrated cation form of the application. For example, the cation exchange membrane used in chlor alkali cells can fail to pass significant amounts of electrical current until equilibration has occurred to the hydrated sodium ion form of the membrane. U.S. Pat. No. 3,985,631 to Hora et al teaches a chemical pretreatment for chlor alkali cation exchange membrane that results in the introduction of hydrated alkali metal ions substantially throughout the membrane. U.S. Pat. No. 4,333,810 to Wolcott et al teaches preconditioning the cation exchange membrane of a sensor for chemical analysis by exposure to a high concentration of the analyte. The above mentioned patents are fully incorporated herein by reference.
Despite the generally good effectiveness of the preconditioning taught by Wolcott et al, the present inventors noted that the sensor's response was not completely stable until the sensor had been in use for many months.
The present invention is an electrolytic method for the pretreatment of a cation exchange membrane so that the membrane's performance is more stable in use.